The present invention relates to a charged particle beam exposure system, such as a lithography system for maskless image projection, scanning and non-scanning electron microscopes, and the like.
Charged particle beam lithography systems, such as electron beam maskless lithography systems, are generally known and, relative to conventional mask based lithography systems, have the advantage of fabrication on demand as it were, due to an absence of the necessity to change and install masks or reticles. In stead, the image to be projected for the manufacture of integrated circuits is stored in a memory of a computer that controls the maskless exposure system.
The known charged particle beam exposure systems commonly comprise a charged particle column placed in a vacuum chamber. The charged particle column comprises a charged particle source including a charged particle extraction means and electrostatic lens structures for the purpose of focussing and deflecting one or a multiplicity of charged particle beams on and over a target, such as a wafer. Furthermore the charged particle column comprises modulation means for modulating the one or multiplicity of charged particle beams, depending whether the image to be projected requires an exposure at a certain location or not.
During such projection the target is guided relative to the projection area of said charged particle column, by means of a stage that supports the target. For this new type of maskless lithography, appropriate stages have hardly been designed, at least are not commercially available. Known stages, for as far as they can be adapted to maskless lithography, are mostly inappropriate at least in the sense of e.g. size, costs and vacuum compatibility.
Also electromagnetic dispersion fields as commonly present at actuators, in particularly electro-magnetic actuators, are normally not desired in such systems, because any variation in electric of magnetic fields may affect the position of charged particle beams. It is known that fluctuations in electromagnetic fields due to an electromagnetic actuator can be reduced by arranging the electromagnetic actuator at a position remote from a target-bearing surface and providing a multiple shield in the electromagnetic actuator.
It is an object of the present invention to provide a charged particle beam lithography system comprising and an operating method using a target positioning device optimized for charged particle beam exposure of a target.